Fujitsu Corporation

Yohei Sobu

Shinsuke Tanaka

Tomoyuki Akiyama

An optical transmitter transmits a modulated optical signal in which each symbol carries M bits. M is an integer larger than one. The optical transmitter includes: a signal generation circuit configured to generate M&#xd7;N binary electric signals based on transmission data, bit rates of the M&#xd7;N binary electric signals being equal to each other, N being an integer larger than one, when the optical transmitter multiplexes N optical signals in time-division multiplexing; a Mach-Zehnder interferometer; and M&#xd7;N phase-shift elements provided along an optical path of the Mach-Zehnder interferometer and respectively configured to shift phases of light propagated in the optical path corresponding to the M&#xd7;N binary electric signals. The M&#xd7;N phase-shift segments are comprised of N electrode groups. Each of the N electrode groups includes M or more electrodes to which corresponding M binary electric signals among the M&#xd7;N binary electric signals are given.

Optical transmitter for transmitting multilevel optical signals

An optical modulator, that includes a Mach-Zehnder interferometer and three or more segments, generates an optical signal based on three or more electric signals transmitted in parallel. The three or more segments are provided in series along an optical path of the Mach-Zehnder interferometer and respectively shift a phase of light propagating through the optical path based on the three or more electric signals. A length of at least one of the three or more segments is different from lengths of the other segments. Optical path lengths from input ends of respective segments to input ends of corresponding next segments are the sae.

Optical modulator and optical modulation method

An optical semiconductor device includes a first optical coupler including a first input port and a second input port, a first optical branching device including a first output port and a second output port, a second optical coupler including a third input port and a fourth input port, a second optical branching device including a third output port and an fourth output port, a first single mode waveguide configured to connect the second input port and the first output port, a second single mode waveguide configured to connect the second output port and the third input port, a third single mode waveguide configured to connect the fourth input port and the third output port, and a fourth single mode waveguide configured to connect the fourth output port and the first input port.

Optical semiconductor device and reception apparatus

A transmission device including a multi-division optical modulator having a plurality of modulation segments, the transmission device includes a driver circuit configured to output binary data for each bit based on an input electrical signal, and an optical modulator configured to have a multilevel modulation segment driven by a first drive signal including two or more bit signal from the driver circuit, and plural binary modulation segments driven by second drive signal including only one bit signal from the driver circuit, wherein the multilevel modulation segment incudes a first phase shifter disposed on each arm of the optical modulator, the binary modulation segment includes a plurality of second phase shifters arranged along each arm of the optical modulator, and lengths of the second phase shifters are all the same and are shorter than a length of the first phase shifter.

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Chiyoda, Japan

Yohei Sobu